Phosphine in Venus's atmosphere: evidence of life or chemistry?

Discussion in 'Chemistry' started by Peter Dow, Sep 15, 2020.

  1. Peter Dow Registered Senior Member

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    The BBC and reputable news agencies like Reuters are hyping claims that the detection of phosphine in the atmosphere of Venus "could be" evidence of life on Venus.

    Are they right or don't they know their chemistry?

    P4(g) + 6H2O(g) + 6CO(g) → 4PH3(g) + 6CO2(g)
     
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  3. exchemist Valued Senior Member

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    Hmm, I'm not sure why the reaction you post would be relevant. What makes you think gaseous elemental phosphorus would be expected in the Venusian atmosphere?
     
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  5. Sarkus Hippomonstrosesquippedalo phobe Valued Senior Member

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    You do know that chemistry doesn’t work just because you can balance each side of the supposed reaction with equal numbers of each element? Care to explain under what conditions those molecules are supposed to interact to combine the carbon dioxide and phosphine? Why is the carbon monoxide needed, when phosphorous can react directly with water? And why not react directly with hydrogen?

    But I’m sure you are going to explain all this, right?

    As for hyping, sure, it’s how they make their money. But they are right, in that it could be produced biologically in the atmosphere of Venus. They have ruled out some of the more obvious means of producing the gas, but since they don’t know everything about Venus, there is always the option of a geophysical cause, or something else.
    What they also don’t actually tell you, though, is that microbes aren’t yet proven to produce phosphine biologically. It is widely thought to be the breakdown of certain biomass that gives rise to it, not the biological activity of that biomass itself. But more testing in labs is needed.

    But please, do explain your reaction and how you think it actually works.

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  7. Peter Dow Registered Senior Member

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    The overall reaction looks plausible to me if we experimentally mix phosphorus with water and carbon monoxide at the pressure (92 bar) and temperature (464 °C) found at or near the surface of Venus.

    If experimentally some phosphine is produced in such conditions then such a finding would suggest the reaction is likely to be more relevant to what's happening on Venus than wild theories of "life on Venus".

    Water and carbon monoxide are present in the atmosphere of Venus
    There's no hydrogen or oxygen in the atmosphere of Venus so I've not suggested those as initial reactants or final products.

    Elemental phosphorus on the surface of Venus I have no evidence for, admittedly, so the phosphorus for my reaction may be sourced from some other precursor phosphorus compound or phosphorus-rich mineral.
     
    Last edited: Sep 15, 2020
  8. DaveC426913 Valued Senior Member

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    A key component to this mystery is not simply that phosphine is found - but that it is found in a significant concentration suggesting it's being continually produced - as Venus' atmo is going to break it down almost as soon as its produced. So what''s producing it in such quantities?
     
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  9. exchemist Valued Senior Member

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    Elemental phosphorus is most unlikely to be present on Venus. The atmosphere is full of sulphuric acid, which as well as being acid is quite a powerful oxidising agent. Most likely, phosphorus would be present on Venus in oxidised form, as phosphate or phosphite minerals, or possibly even as free phosphoric acid in the clouds, along with the sulphuric acid.

    If so, you would need a reducing reaction to generate phosphine. Interestingly, I see from looking it up that phosphorous acid (H3PO3) can disproportionate into phosphine and phosphoric acid:
    4 H3PO3 -> PH3 + 3H3PO4

    So that might be one pathway. But it will be this need for a reduction reaction that leads the researchers to wonder about bacteria.

    P.S. You can also generate phosphine by hydrolysis of phosphides, but where and how would phosphides form? Some volcanic process, under reducing conditions, maybe?
     
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  10. Michael 345 New year. PRESENT is 70 years old Valued Senior Member

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    Thought it found in the clouds at about 40°C. I didn't get the pressure

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  11. exchemist Valued Senior Member

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    Good point.

    I must say I rather like the idea that we've all been searching for life of the wrong sort, in the wrong place, i.e. on the surface, on Mars. It would be just like the universe to make jackasses of us by developing aerial life, on a planet with a surface temperature of 400C and clouds of sulphuric acid.

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    But this phosphine discovery is a very long way from real evidence of life, of course.
     
  12. Michael 345 New year. PRESENT is 70 years old Valued Senior Member

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    https://www-nytimes-com.cdn.ampproj...com/2020/09/14/science/venus-life-clouds.html

    Bit more information

    And near the middle of the cloud layer, temperatures and pressures are rather Earthlike. “It’s shirt-sleeve weather, with all these tasty things to eat,” says Martha Gilmore, a Wesleyan University planetary scientist and leader of a proposed mission to Venus, referring to molecules in the planet’s air that microbes could metabolize.

    https://api-nationalgeographic-com....0043438&csi=1&referrer=https://www.google.com

    The plot thickens

    And I am being distracted again

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    Curse being stuck in Bali

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  13. Peter Dow Registered Senior Member

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    Agreed.

    Which suggests the chemical reactions -

    P4O6 + 6 H2O → 4 H3PO3 → 3 H3PO4 + PH3

    Those reactions cited from -

    https://en.wikipedia.org/wiki/Phosphorus_trioxide#Chemical_Properties

    https://en.wikipedia.org/wiki/Phosphorous_acid#Disproportionation
     
  14. exchemist Valued Senior Member

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  15. Peter Dow Registered Senior Member

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    I didn't state or imply that I thought that particularly.

    What I quoted was this

    "clouds" aren't on the surface. The quote doesn't say anything about the surface. I didn't say anything about the surface in relation to P4O6. You seem to be the only person here who has mentioned P4O6 in relation to the surface.
     
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  16. exchemist Valued Senior Member

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    Oh I see.

    That section seems to have been added to the Wiki article in the last 48hrs. At any rate I don't recall seeing it when I last looked at it.

    I'm now trying to find out what the Vega mission actually found. It seems suspicious to me that the authors of this new work would have failed to spot something so obvious, if the Vega mission really did find P4O6 and phosphorous acid were present.
     
  17. Michael 345 New year. PRESENT is 70 years old Valued Senior Member

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    But scientists have suggested simple life forms could take refuge high in Venus’s atmosphere, where temperatures and pressures are similar to conditions found at sea level on Earth. Astronomers announced Monday that observations through ground-based telescopes detected phosphine in Venus’s clouds.

    Phosphine, made by combining a phosphorus atom with three hydrogen atoms, is only generated on Earth from microbes and industrial activity, scientists said. While a sliver of Venus’s atmosphere has the right temperature and pressure to harbor life, the region strewn with droplets of sulfuric acid and lacks water.

    MY HIGHLIGHTS

    https://spaceflightnow.com/2020/09/...-a-privately-funded-probe-could-lead-the-way/

    Nothing to do with Vega

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  18. exchemist Valued Senior Member

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    Actually I have looked this up and it is true that one of the Vega workers wrote a paper back in 1988 that said P4O6 is present in the Venusian clouds: https://www.sciencedirect.com/science/article/abs/pii/0019103589901681

    The curious thing is that this latest paper in Nature which has caused all the current ballyhoo: https://www.nature.com/articles/s41550-020-1174-4
    states that the Vega probe was only able to identify phosphorus as an element, rather than in what chemical compounds it was present! They go on to dismiss the possibility of H3PO3 in the clouds, as it would not be fully oxidised, whereas with all that sulphuric acid about it is a highly oxidising environment.

    So I am left to wonder whether the writers of the Nature paper have overlooked this Vega finding. If so, that could be very embarrassing for them.

    Alternatively, they may have convinced themselves the Vega paper is wrong. However the fact they don't reference it, even to dismiss it, suggests that isn't the explanation. But they do provide considerable supplementary information on the modelling they have done of thermodynamics and kinetics of various reactions, involving H3PO3 and conclude it can't be responsible: https://static-content.springer.com...4/MediaObjects/41550_2020_1174_MOESM1_ESM.pdf

    There seems nevertheless to be a loose end here that could turn out to be important. Someone needs to tackle the issue of the Vega paper, either to take it seriously or to dismiss it.

    Interesting!
     
    Last edited: Sep 18, 2020
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  19. Michael 345 New year. PRESENT is 70 years old Valued Senior Member

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  20. exchemist Valued Senior Member

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    What an extraordinary source. It seems to be written in hilarious gibberish.

    Specimen: "To create the observed quantity of phosphine (which consists of hydrogen and phosphorus) on Venus, terrestrial organisms would only got to work on about 10% of their productivity, consistent with the team." ???

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    Translated from Japanese by a bot? Anyway, incomprehensible. Did you actually read this shit? Just posted it for a laugh, I suppose.

    I vill not buy zees tobacconist, it eez scratched.

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  21. Michael 345 New year. PRESENT is 70 years old Valued Senior Member

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    Skimed it. At the moment I was busy being distracted

    Zee tobacconist, is zee tobacconist African or European?

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  22. exchemist Valued Senior Member

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    Not Hungarian, evidently:
     

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